TouchCe Definition

# Do Circles C1 and C2 touch?
# It first solves the equation C1=C2, plugs the solution into C1 and determines whether the discriminant
# of the resulting quadratic is zero.

TouchCe:=proc(C1,C2) local q:

q:=expand(subs(y=solve(C1-C2,y),C1)):

ItIsZero (4*coeff(q,x,2)*coeff(q,x,0)-coeff(q,x,1)^2):

end: